Abstract:

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A new algorithm is proposed to determine the through-thickness residual stress gradient
by X-ray Diffraction measurements on progressively thinned components. The procedure is based
on a chemical or electrochemical attack of the component surface, which is then measured at each
thinning stage. The simple algorithm provided for by a specific norm has been revised to take into
account the X-ray absorption effects and the conditions of mechanical equilibrium of the
component. The new procedure is illustrated for a typical case of study concerning a shot-peened
metal component.

Abstract: The work hardening effect of the shot peening affected layer of hardened and low
temperature tempered spring steel was investigated using the method for determining the yield strength of a metallic surface with biaxial residual stress. The results show that for the surface layer of the specimens, the microhardness and half-width values of X-ray diffraction lines is decreased, whereas the yield strength is increased during shot peening. Thus, shot peening leads the surface layer of steel in hard state to work hardening instead of work softening.

Abstract: We attempted to estimate the residual stress which evolved during the shot peening of Al
7075 alloy using leaky surface acoustic wave (LSAW). Shot peening was conducted to produce a
variation in the compressive residual stress with the depth from the surface at a shot velocity of 30m/s.
The LSAW velocity was measured using a scanning acoustic microscopy (SAM). The Vickers
hardness profile obtained inwards from the surface showed significant work hardening of the near
surface layer with a thickness of about 0.3mm. The variation in the LSAW velocity through the shot
peened surface layer was in good agreement with the distribution of the residual stress measured by
X-ray diffraction.

Abstract: The strain scanning method was applied to the evaluation of the subsurface distribution of
the residual stress beneath the shot-peened surface of an austenitic stainless steel SUS304L which had
coarse grains and preferred orientation. The experiment was performed at beam line BL22XU at
SPring-8 using monochromatic X-rays of 70.14 keV and a Ge (111) analyzer. The sizes of both
incident and receiving slits were 2 × 0.2 mm2. The specimens were annealed or shot-peened and had
the dimensions of 20 × 20 × 5 mm3. The grain size was about 37 μm. In order to obtain the diffractions
from an enough number of grains, various types of oscillation methods, which were translation,
rotation and tilting of the specimen, were examined. The translational oscillation was found to be
enough to obtain the accurate strain distribution. By combining the translational oscillation method
with the correction to the surface aberration, the subsurface distribution of the residual stress of
shot-peened austenitic stainless steel was successfully determined.

Abstract: The residual stress profile in a shot-peened Al alloy component was studied by a recently proposed method based on the known procedure of progressive thinning and X-ray Diffraction measurements. The effect the cyclic stress on the fatigue life was studied in detail, showing the correlation between nominal load and residual stress relaxation. Besides showing the expected decrease of compressive stress with the load and number of cycles, the present work highlights the importance of changes in the through-the-thickness residual stress distribution.

Abstract: Laser shock peening offers potential advantages over conventional peen technologies in terms of the depth of the residual stresses that can be induced, and improvements in surface roughness. In this study the application of laser peening to thin aluminium plates such as are used in aerospace applications is investigated. Peening of thin plates presents challenges in balancing the peen intensity to prevent overpeening that will actually lower the stress field. Strain profiles for different laser peening parameters were obtained using synchrotron X-ray diffraction at the ESRF, France. Results are presented and discussed of the residual strain profiles in terms of the laser power density and the number of peen passes. When the power density and number of passes are increased the compressive strain magnitudes are also increased, as has been observed in previous studies. However, the strain components longitudinal and transverse to the peen line are not identical to each other, with the transverse component being much less compressive.